Model for an optically thick torus in local thermodynamic equilibrium around a black hole

Zanotti, Olindo

doi:10.1051/0004-6361/201323334

A&A

2014

DOI: 10.1051/0004-6361/201323334

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Model for an optically thick torus in local thermodynamic equilibrium around a black hole

Olindo Zanotti

Abstract: We propose a simple model for an optically thick radiative torus in local thermodynamic equilibrium around a Kerr black hole. The hydrodynamics structure, which is not affected by the radiation field, is the same as for the so-called polish doughnuts. Under the assumption of isentropic fluid and polytropic equation of state, a simple stationary and axisymmetric solution to the relativistic radiation hydrodynamics equations is possible, for which the temperature of the torus scales like the specific enthalpy. T… Show more

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Cited by 3 publications

(2 citation statements)

References 38 publications

(55 reference statements)

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“…A truly equilibrium model for a thermodynamic torus around a black hole, which is however not valid for ideal gas equations of state, has been described inZanotti (2014). 2 Such a setup effectively prevents the torus from being self-illuminated, which could in principle affect (and complicate) its dynamical behaviour.…”

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confidence: 99%

Oscillations of radiation pressure supported tori near black holes

Mazur¹,

Zanotti²,

Sądowski³

et al. 2016

Mon. Not. R. Astron. Soc.

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We study the dynamics of radiation pressure supported tori around Schwarzschild black holes, focusing on their oscillatory response to an external perturbation. Using KORAL, a general relativistic radiation hydrodynamics code capable of modeling all radiative regimes from the optically thick to the optically thin, we monitor a sample of models at different initial temperatures and opacities, evolving them in two spatial dimensions for ∼ 165 orbital periods. The dynamics of models with high opacity is very similar to that of purely hydrodynamics models, and it is characterized by regular oscillations which are visible also in the light curves. As the opacity is decreased, the tori quickly and violently migrate towards the gas-pressure dominated regime, collapsing towards the equatorial plane. When the spectra of the L 2 norm of the mass density are considered, high frequency inertial-acoustic modes of oscillations are detected (with the fundamental mode at a frequency 68M −1 BH Hz), in close analogy to the phenomenology of purely hydrodynamic models. An additional mode of oscillation, at a frequency 129M −1 BH Hz, is also found, which can be unambiguously attributed to the radiation. The spectra extracted from the light curves are typically more noisy, indicating that in a real observation such modes would not be easily detected.

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mentioning

confidence: 99%

Oscillations of radiation pressure supported tori near black holes

Mazur¹,

Zanotti²,

Sądowski³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Though rather simplified, geometrically thick discs are still attracting a lot of interest in high energy astrophysics. From one side, they are currently adopted as initial conditions in general relativistic hydrodynamic and magnetohydrodynamic numerical simulations of accretion flows [44,21,9,32,28], even in the presence of radiation fields [41,29,47]. Moreover, an additional indication supporting their astrophysical relevance is provided by the outcome of fully relativistic numerical simulations, which clearly show that high-density tori are indeed produced after the merger of neutron star binaries collapsing onto a black hole [39].…”

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confidence: 99%

Von Zeipel’s theorem for a magnetized circular flow around a compact object

Zanotti

Pugliese

2015

Gen Relativ Gravit

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We analyze a class of physical properties, forming the content of the so-called von Zeipel theorem, which characterizes stationary, axisymmetric, non-selfgravitating perfect fluids in circular motion in the gravitational field of a compact object. We consider the extension of the theorem to the magnetohydrodynamic regime, under the assumption of an infinitely conductive fluid, both in the Newtonian and in the relativistic framework. When the magnetic field is toroidal, the conditions required by the theorem are equivalent to integrability conditions, as it is the case for purely hydrodynamic flows. When the magnetic field is poloidal, the analysis for the relativistic regime is substantially different with respect to the Newtonian case and additional constraints, in the form of PDEs, must be imposed on the magnetic field in order to guarantee that the angular velocity Ω depends only on the specific angular momentum ℓ. In order to deduce such physical constraints, it is crucial to adopt special coordinates, which are adapted to the Ω = const surfaces. The physical significance of these results is briefly discussed.

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Relativistic thick accretion disks: Morphology and evolutionary parameters

2015

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We explore thick accretion disks around rotating attractors. We detail the configurations analysing the fluid angular momentum and finally providing a characterization of the disk morphology and different possible topologies. Investigating the properties of orbiting disks, a classification of attractors, possibly identifiable in terms of their spin-mass ratio, is introduced; then an attempt to characterize dynamically a series of different disk topologies is discussed, showing that some of the toroidal configuration features are determined by the ratio of the angular momentum of the orbiting matter and the spin mass-ratio of the attractor. Then we focus on "multi-structured" disks, constituted by two o more rings of matter orbiting the same attractor, and we proved that some structures are constrained in the dimension of rings, spacing, location and an upper limit of ring number is provided. Finally, assuming a polytropic equation of state we study some specific cases.K ∈]0, 8/9] there are the solutions ( = 0, y = 3M ) and ( > 0, y = M ), see Figs. (18). The limiting case = 0 is shown here, with increasing a B-configuration emerges.

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Model for an optically thick torus in local thermodynamic equilibrium around a black hole

Cited by 3 publications

References 38 publications

Oscillations of radiation pressure supported tori near black holes

Oscillations of radiation pressure supported tori near black holes

Von Zeipel’s theorem for a magnetized circular flow around a compact object

Relativistic thick accretion disks: Morphology and evolutionary parameters

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